Method of working metal



$epi. 4, 1923.

E. G. LOOMIS METHOD OF WORKING METAL Filed 001:. s, 1920 (gyzvm/e m- A T ORA 5w,

" when finishing holes inlarge quantities.

Patented Sept. 4, 1923.

UUNHTED STATES EVABTB G. 1001118, 01 NEWARK, NEW JERSEY.

METHOD OF WORKING METAL.

Application filed October 8, 1820.; Serial No. 415,570.

To all whom it may concern:

Be it known that I, EVARTS G. 11001113, 9. citizen-oi. the United of Newark,-county of Essex, State of New Jersey, have invented certain new and useful Improvements in Methods of Working Metal, of which the following is a specification.

. My invention relates in general to an imgproved method.for working metal and is particularly directed to a method for finishmg holes in metal or other rigid material whereby much better results are obtained than now possible and whereby a saving is efli'ected in the metal itself.

An object of my invention is to the provision of a method whereby holes may be finished in metal bushings and bearings for example much more smoothly than now possible and may be located much more accurately than under the present practice.

In order that my improved method may be clearly understood I will refer briefly to the finishing of holes in metal as now practised. Under the present practice the hole after being cast is broached. In the casting operation the hole is necessarily tapered for draft and furthermore is more or less out of round and the walls of the hole contain more or less sand. It therefore becomes necessary to true up the hole and also to remove the scale and sand in the walls, thereby necessitating the removal of a suificient amount of metal to leave a smooth finish. The broach employed. of course, has several cutting zones and in practice the first cut must be heavy enough to remove a sufiicient amount of metal from the walls of the hole to elimihate the scale, sand and irregularities therein and thereon, otherwisethe broach would be dulled so rapidly as to make its use impracticable. The first cut taken by the broach is therefore necessarily very heavy. As the result .of this heavy cut the hole'is shortened appreciably due to the compression of the metal in taking this cut. It has been found also that the metal is torn where the broach leaves the hole. The finished piece, of course, must be of a certain predetermined length and for this reason allowance must be made for the shortening of the hole and the tearing out of the metal at the end of the hole, pointed out above. In other words, some metal is wasted in the finishing of each hole which amounts to a great waste States, and a resident h Furthermore, owing to the great pressure necessary to force the broach through the ole by reason of the heavy cut, a great deal of heat is generated causing both the hole and the broach to be deformed. It has been found also that owing to this'heavy cut it is exceedingly diflicult to locate the hole accurately, probably due to the springing of the broach in the broaching operation.

In the practice of my improved method I employ first of all a tapered tool, that is to say a tool the diameter of which gradually diminishes in a given direction, such as a hardened steel ball for example, in the case of a round hole, slightly larger in diameter than the cast hole. This tapered tool is forced through the hole from one end to the other and in passing through irons out, as distinguished from'cutting the irregularities on the surface of the wa ls of the hole.

I find also that. in using this tool the walls of the hole are made smooth and parallel and are brought to approximately the desired form. The texture of the metal constituting the walls of the hole is improved also due to the compressing of the metal for it is to be understood that the tapered tool expands the hole without removing metal therefrom. After the first tool has been passed through the hole I preferably, though not necessarily, pass one or more similar tools through the hole each of which is of slightly larger diameter than the preceding tool so that the pressure employed is brought within limits which will not cause the hole to be shortened or the metal heated appreciably.

I follow this operation (or operations) with a broaching operation, the broach, due to the fact that the hole by this time is almost the required size and form, removing but a very small portion of metal from the walls of the hole,in fact just sufiicient to remove the scale and sand on the walls of the hole and to straighten the hole. I preferably, though not necessarily, after the broaching operation, pass a spherical tool through the broached hole which tool would still further iron out the walls of the hole and be of a size to bring the hole to the exact desired dimension. The purposeof this last operation is to make more dense the metal constituting the walls of the hole.

In the accompanying drawings, I have illustrated the finishing of a hole in a metal bushing for example by the old method and 'the finishing of a, hole in a metal bushing for example by my improved method. Figs. 1 and 2 illustrate the old method, while Figs. 3, 1 and 5 illustrate my improved method.

Referring to Figs. 1 and 2, 1 designates a metal bushing which is cast with a tapered hole, 2, but with straight side walls, 3. Under the old methods, it is customary to force a broach, designated 4, through the tapered hole 2 in order to remove the scale on the walls of the hole and to straighten the hole. I have indicated by dotted line 5 the walls of the hole 2 after the broach 4 has been operated. Fig. 2 indicates the condition of the bushing 1 after the hole 2 has been broached. It will be seen from Fig. 1

that a very heavy 'cut is necessarily taken with the broach 4 in order to remove the scale from the Walls of the hole 2 and to straighten the hole. Due to the fact that this very heavy cut must be taken, it has been found in actual practise that the bushing is materially shortened after the broaching operation Fig. 2. It will be seen also that the outside of the bushing has been deformed and that the metal adjacent to the lower end of the hole 2 has been broken away by the broach. The result of all of this is that after the hole 2 has been finished as indicated in Fig. 2 it becomes necessary to finish the outside of the bushing up to about the dotted line 6 and the lower end of the bushing must be turned off up to the dotted line 7. All of the metal that is thus removed in the finishing operation is wasted. It is to overcome this inefiicient method of finishing holes that the present method has been devised.

Referring now to Figs. 3, 4: and 5, which, as I have noted, illustrate the various steps of my improved method, 8 designates a bushing to be finished and from Fig. 3, it will be seen that this bushing is cast with a tapered hole 9, which is the hole to be finished,

'of course, and tapered side walls 10. The

exterior and interior surfaces of the bushing are practically parallel to each other. In the first step of my improved method, I force a steel ball 11 through the hole 9 which irons the walls of the hole and also straight ens the hole and forces out the exterior surface of the bushing, so that after the ball 11 has been forced through the hole 9, the bushing has the appearance indicated in Fig. 4. Up to this point, no metal has been wasted at all. It then remains merely to broach the hole with the broach 12, cutting the hole back to about the dotted line 13, which is merely far enough back to remove the scale on the inside of the hole. So far as the hole 9 is concerned, it is finished after the broach 12 has passed through. As the surface 10 of the bushing has not been deformed in any wa whatsoever, it is merely necessary to turn own the same to about the dotted line 14 and to turn off the ends to the ticularly well adapted for working bronze and inasmuch as bronze is a comparatively expensive metal it is of material advantage to eliminate waste of this metal as far as possible.

It will be apparent from theforegoing that by my improved method the exterior dimensions of the castin I in which the hole is being finished, particufarly in the case of an article such as a bushing, is increased by the expanding action of the tapered tools. This metal which is gained in the exterior of the casting by this process is available for finishing the exterior of the casting. It will therefore be possible with this new method to use less metal inthe initial casting, for with the former process as outlined above, the exterior of the casting is not uniformly increased and the material which is cut out from the hole is entirely wasted and is not available for finishing off the exterior of. the casting.

In actual practice I find that by my method it is much easier to locate the hole centrally. for example in the case of a bushing, than by the methods now practised. This is apparently due to the fact that the tapered tools employed by me follow the initial hole and iron out and expand the hole whereas under the old practice considerable metal is removed in the broaching operation and for this reason great pressure must be exerted on the broach which in practice deforms not only the broach but the casting itself.

It is to be understood that in the practice of my improved method I am not to be limited to the use of a steel ball inasmuch as obviously substantially the same results can be obtained by employing any tapered tool that is a tool the diameter of which gradually diminishes in' a given direction andwhich expands the hole as distinguished from removing metal therefrom. I prefer, however, to employ a hardened sphere as such a tool has an indefinite number of work ing surfaces and is comparatively inexpensive to manufacture and maintain.

What I claim is:

1. The method of finishing a hole in a metal member, which method consists in passing a spherical tool through the hole to be finished and thereafter broaching the hole.

2. The method of finishing a hole in a rigid member which method consists in first passing a tool through the hole to compress the metal surrounding the same and there- 5 after removing the scale from the Walls of the hole.

3. The method of finishing a hole in a metal bushing which method consists in first passing a ball or sphere through the hole to be finished to straighten the hole and to iron out the Walls thereof and thereafter broaching the hole to remove the scale from the Walls thereof.

This specificationsigned this 7th day of October, 1920.

EVARTS G. LOOMIS. 

